1. Field of the Invention
The present invention relates to a supporting-substrate contact technique in a semiconductor device having SOI structure.
2. Description of the Background Art
In a SOI structure, a device is formed in a SOI layer on a BOX oxide film. Hence, a contact needs to be formed to reach a supporting substrate so as to fix the substrate potential (cf. Japanese Patent Application Laid-Open No. 2001-28438 or 2001-44441).
On the other hand, a mounting technique of semiconductor components has been developed into a flip-chip (FC) technique of mounting a bare semiconductor chip directly on a substrate. When applying such FC technique to a semiconductor chip having SOI structure, the rear surface of the semiconductor chip, i.e., the bottom of a supporting substrate in the SOI structure is present on the front surface side to be exposed (that is, the front surface of the semiconductor chip is positioned on the rear side), which arises the need to fix the potential of the supporting substrate to a ground potential. However, various structures presented by conventional techniques are not intended to cope with such case, which are thus not applicable to such mounting.
Further, the SOI structure tends to be increased in contact resistance with size reduction of the device and with decreasing processing temperature.